|
%I #12 Jan 22 2024 13:02:59
%S 72,9711,997101,99731009,9999110007,999983100003,99999911000003,
%T 9999998910000019,999999937100000007,99999999671000000007,
%U 9999999997710000000019,999999999989100000000003,99999999999711000000000039,9999999999997310000000000037
%N Concatenation of the largest and the smallest n-digit primes (in that order).
%H Chris Caldwell, <a href="http://www.utm.edu/research/primes/lists/small/10000.txt">The First 10,000 Primes</a>.
%e The largest and smallest 1-digit primes are 7 and 2, so the first term is 72.
%e The largest and smallest 2-digit primes are 97 and 11, so the second term is 9711.
%p for n from 0 to 30 do for m from 1 to 10^(n+1)-1 do if isprime(10^(n+1) - m) then printf(`%d`,10^(n+1)-m); break; fi: od: for m from 1 to 10^(n+1)-1 do if isprime(10^n + m) then printf(`%d`,10^n+m); break; fi: od: printf(`,`): od: # _James A. Sellers_, May 02 2005
%t Table[FromDigits[Join[IntegerDigits[NextPrime[10^n,-1]],IntegerDigits[NextPrime[10^(n-1)]]]],{n,14}] (* _James C. McMahon_, Jan 22 2024 *)
%Y Cf. A104206.
%K nonn,base
%O 1,1
%A _Parthasarathy Nambi_, Apr 30 2005
%E More terms from _James A. Sellers_, May 02 2005
%E Offset corrected by _Michel Marcus_, Aug 18 2017
%E a(13)-a(14) from _James C. McMahon_, Jan 22 2024
| 